Vehicle brake



\ Aprii21,1942. www .2,280,134

` VEHICLE BRAKE' l FiledJan. 11, 1959- 2 Sheets-Sheet 1 5. Nw, H Rd ,mW N mh T H www. MNMU, a@ u, f. ,f w

\hv\ WN MQ l MW SN. Nh l v ww April 2l, 1942. G. J. THOMAS s 2,280,134

y l VEHICLE BRAKE Filed Jaml ll, 1939 2 Sheets-Sheet 2 ATT je; 676156? .'53

Patented .1\pr.i: .1,1942` Y PATENT eFH-CE vEHicLE BRAKE d `jGfeorge Joseph Thomas, Detroit, Mich.

ApplicationJanuar-iii, 1939, serial No. 250,291l

` (orgias-47,8) I d a brake structure whichincludesa hydraulically d 10 Claims.

This invention relates to vehicle brakes Iofthe internal expanding type which kare operated either mechanicallyorhydraulically e One of the objects of the invention is to pro.-

vide an improved brake structure `in.v. rl iich `the `brake operating forceis .distributed to different -parts of `the shoe by improved self-actuating mechanism whichais responsive tothe brakeap` i plicaticn force.

Another object `of the invention is to1 provide a brake oftheforegoing character `in Whichvzthe self-actuating or brake energizing `mechanism' is cient in operation.` I. A l l A furthergobject of theinvention isfto provide `of `relatively simple construction and more eff a brake structure includingga transversely split brake shoeor brakeqband adaptedfor engagement with a brake drum,\ the shoe being expanded or applied by the application of force `to the split end portions `thereof` and; energizing means, in-

`cluding for, example a rockable device located at a point intermediate the ends of` thelshoe and preferably mounted upon the anchor pin, being force I for exerting pressure simultaneously 1 ai;v a plurality of spaced points on the ,shoe `thereby more i uniformly distributing the. pressure be` required to i provided and responsive to the brakeapplication tween `.the shoe or brake bandand the drum and actuated by the application` of force tothei split ends of the shoe andhaving energizing means `as- :1

sociated `with the anchor pin and responsive to the brakeapplication force for exerting pressure y upon the shoe simultaneously at opposite sides of the anchor pin. i i

A still further'object of.` vthe invention is to pro. vide an improved` vehicle brake having a split brake shoeand means zior Aamilyingpressure to the shoe at two points adjacent the split ends of` the shoe to apply the brake and also including self-energizing means `actuated by rotative movei ment of the brake4 shoe =to` `simultaneously apply pressure to the shoe;at twoipointsintermediate the split endsgthereof.;

A further object of `the invention vis toprovide improved self-actuating mechanism for transmitting the force applied tothe brake shoe si` multaneous'lytoa plurality ofyspaced points of the brake shoe remoteiromthe original point or points of application pt lthe force `to said shoe.

i Affurther `object ofi` the;invention` is to `provide actuated wheel cylinder of improved construction. j i

A still further object o the invention is to pro- -videja wheel cylinder having improved easily 'accessible adjusting means forvarying the position of the brake shoe with relation tothe brake drum.

The above and other objects and advantages of the invention will appear yfrom `thelfollovving description and appended claimswhen considered drawings `forming apartofthis specication in whichlike reference'characters designate correin `connection with the v accompanying spending parts in the several views.

In said, drawings; y Fig.` lj isl a `vertical sectional View tak-en along the `line-` I -I" of Figi-2, looking in lthe `direction of the-arrows, and showing the lparts in released position. l i

Fig. 2 -is a vertical section; taken through the v center `of the brake structure shown Ain Figi 1.

5 of Fig. 1,v looking in the direction of the arrows;

and l Fig. 6 is anenlarged fragmentary section of the wheel cylinder of the preceding views show- `ing the parts in brake applied position.

Before explaining in detail the present invention it is to b e understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated lin the accompanying drawings, since the invention is capable of other/embodiments and of being practiced or carried out in various ways; Also it is to beA understood that the phraseology or terminology employedherein is for `the purpose of description and not oflimitation, and it` is not intended to limit the inventionclaimed herein beyondthe requirements of the prior art. jV i Referringnow to the drawings, the brake construction of the present invention, as shown, comprises a brake drum I0- which is secured to the wheel hub II `by means of boltsor thelike I2. Al suitable backing plate I3 for closing the end of the drum is securedby means `of bolts andnuts I5 to the axle housing shown generally at I4..A An

A anchor pin I6 is mounted in the backing plate I3 v central portion 4Ia of the spring plate.

through a hole or opening in the plate and is secured to the plate by a nut I1. The anchor pin, as will be presently described, is provided for the purpose of supporting the actuating or energizing mechanism described in detail below.

The brake includes a one-piece brake band or shoe I8 provided preferably at a central point with a slot or recess I 9. The metallic brake band or shoe I8 is flexible throughout its length and is provided with a suitable brakel lining 23. opposite sides of the slot or recessl I3 tliebrake shoe I8, on its inner face, is provided with stepped lugs or projections 2l and 22.

provided with opposed lugs or projections 23 hav- The free ends ofi the shoe are spaced apart a suitable distance and..

ing reduced ends or heads 24 each 'of' which -is provided with convex faces 25, see particularlyV Fig. 6. The lugs 23 have hook-like portions 23a to which the ends of coiled springs Zlfare at-E `ment, a double armed lever member shown as a whole at 3U. The member 3U has a central body portion provided with a rounded or arcuate lower end 3l which projects into the slot or recess I9 in the brake shoe, an enlarged upper arm portion 32 and a reduced upward projection 33 having a transverse hole or opening 34 formed therein. The member has outwardly extending arms 35 and 36 which are both adapted to engage the brake shoe when the brake is in the released posiv When the brake is applied, how-I tion of Fig. 1. ever, either one or the other of the arms 35 and 36 will engage the brake shoe to exert pressure thereon in response to the brake applying force.

The self-actuating mechanism also comprises an. energizing member or link shown as a whole at 31 and provided with a central slot or opening 38. The ends 39 and 40 of the link are adapted yto be seated and to engage the shoulders or abutments in the stepped bosses or lugs 2|, and '22; respectively, ofthe brake shoe, see particularly Fig. l. .f-

When the link 31 is assembled with the rockable member 30, the enlarged upper portion 32 of the member is located within the slot 38 of the link. Relative rocking movements of the energizing link and bell crank lever or member 3D are permitted .i

by reason of the curvature of the edges of the portion 32 and a slight clearance thereof in the slot. The link 31 is preferably held down in position with relation to the rockable member 33 by means of a relatively stiff bowed spring plate or leaf 4I which, as seen in Fig. 4, is centrally slotted atV 42 so as to embrace the projecting lug 33 of the rockable member. The spring plate 4I is held in place, so that its opposite ends engage and press against the top face of the link 31, by a pin 43 the central portion 43a of which is rounded and ts within the slot 42, the end portions 43h of the pin having their lower halves removed so as to provide flat faces overlying the enlarged As best Seen in Fig. 5, the central cylindrical portion 43a of the pm is located within the hole sa in the lug' always in operative relation with respect to the energizing member 31.

The ends 39 and 40 of the energizing link are preferably held pressed against their respective lugs 2l and 22 by means of springs 45. Each spring is held in position upon the lugs by a pin 46, the closed or U-shaped portion 41 of the spring overlying the end of the link and the free ends of legs 48 thereof bearing against the inner f ace of the brake shoe. By referring to Fig. 3, in which the position of the rockable member 30 and energizing link 31 may be slightly exaggerated for the purposes of illustrating the action more clearly, it will be seen that while the springs tend' to maintain the ends of the link 31 in con- 'tact with the shoulders or abutments on the r,stepped lugs 2I and 22, when the brake is applied with the wheel rotating for example in a counterclockwise direction, only one end of the link is in Contact with a lug, namely the end 39 engaging the stepped portion of the lug 2I. The spring 45 at the right hand side of Fig. 3 permits the end 40 of the link when tilted slightly to move slightly away from its stepped lug 22.

In the present instance the brake shoe is expanded through the medium of a hydraulic actuator which is located diametrically opposite the anchor pin I6 and located between the ends of the shoe. The actuator, as illustrated in Figs. l, 2 and 6, comprises a cylinder 50 secured to the brake backing plate in any suitable manner. The cylinder is provided with a pair of opposed relatively slidable cup-shaped pistons 5 I. The cylinder at the back thereof is provided with a boss 52 having a passage 53 for the flow of the braking fluid to and from the pressure zone of the cylinder between the inner ends of the pistons. Above the passage `53 the cylinder is provided at the uppermost point thereof with a bleeder passage 54 which is controlled through the medium of a suitable screw threaded valve 55. Within annular grooves in the outer ends of the cylinder bore there are located split resilient wire rings 56 which have snap engagement in the grooves and provide stops for limiting the extreme outward movement of the pistons.

Between each piston 5I and one of the brake shoe lugs 23 is located a two-part transmission or thrust device. The outer thrust member 51 of this device comprises a hollow piece having a cylindrical shank extending axially into the piston and having a rounded or dome-shaped end 51a seated within a correspondingly shaped concave socket 58 formed on the inner face of the head of the piston. The outer end of the member 51 is flared outwardly to provide a frusto-conical portion 59 adapted to engage the chamfered edge at the extreme end of the bore of the cylinder 50. rlhus, engagement of the tapered or flared head 5i) of the thrust membfer 51 with the end of the cylinder bore will limit the inward movement of the piston under the action 'of the return spring 28 when the brake is released.

' The outer thrust member 51 of the thrust device has a central threaded bore 60 to receive a cylindrical exteriorly threaded stem or thrust piece 6 I. The outer end of this member EI has a transverse slot within which theend 24 of the lug 23 fits.

Mounted upon each end of the cylinder is a cup-shaped resilient rubber boot 62 which not only functions to exclude dust and foreign particles but also functions to control the position of the outer thrust member 51. The boot 62 has an annular bead 62a tting into an external groove inl-the cylinder. split spring 'clamping ring-63 assists in holding the :boot upon the end-of the cylinder. The boot 62 also `has an annular inwardly directed webornange portion 62o aper` tured to receive the thrustmember, the `circular edge of `.the aperture fitting lintoa groove 64in ythe outer end of `the member 51. Since `the hole or .aperture in the bottom of the sealing boot 62 has a-slightly smaller diameter than' the diameter 'of the retaining groove 64, the end web 62h ofthe bootwill bedistorted and placed "under stress whenin assembledlpostion, as shown in Fig. 6. `Theb`oot will,` therefore,fact as a frictionallock to gripv and hold the thrustmember 51 in adjusted position against' turning movement. `The end of each lmember 51 is provided with a series of annularly arranged projecting teeth65, preferably wedge-shaped in cross section, and designed for `the reception of a tool to permit turning ofthe clearance. o o i o From thefforegoing it willbe seen that inthe fully retractedpositionsof the pistons, rasiseen in Fig. 1, the pistons will'be centered in the cylinder bore by engagementgof the frusto-.conical heads 59 ofthe pistons withthe end edges of the bore. Whenthe pistons move outwardly under the pressure of. fluid introduced throughthe pas- `sage 53 the members 51 will substantially float,

being Jyieldingly guided andsupported at their outer ends by the resilient rubber `boots 62 and ring extendsradally inwardly beyond the wall of thecylinder. As a result, upon assembly of the `piston with the cylinder by inward movement of the former, the packing ring is` distorted or stressed anda portion thereof is displaced into the triangular portion 61` of the groove, this portion forming a lip facing toward the pressure zone of the cylinder. l

From the foregoing it willbe' seen thatthe packing ringclosely engages both the `cylinder and piston and by reason of thedisplacement of a portion of the packing ring into the lrelieved portion 61 of the groove any pressure=upon the packing ring exerted by the braking fiuid serves to bring `the packingrring more closely into engage-ment with the cylinder and piston. By virtue of this construction, therefore, there is pro vided an annular groove disposed intermediate the ends of the piston with the inner edge of the groove nearer the pressure zone `relieved to provide an annular tapered portionV normally substantially unoccupied by the packing ring, the ring normally when unstressed extending radially inwardly beyond the inner edges of the groovev but being placed in compression when the piston o and cylinder are assembled thereby to displace a o portion of the packing ring in .the` directionof being free for limited universal movement by the l substantially ball `and socket structure 51a and 58.` `Thegboots 62 vhaveisufficient stiffness, however,` to' hold the members 51 approximately centered at all times. o

For fthe purposeof effecting a seal between the pistons 5| and'the cylinder Walls there is provided between each of tli'e pistons and the` annular `wall of the cylinder a packing ring 65. Each atively non-compressible and which may be disable elasticity, which `mayfbe either natural or packing ring is formed of a material whichA is relsynthetic.A Each of the cylinder portions Within i which one of the pistons is located is provided with an annular groove which opens toward the associated piston. 'I'hisannular groove "is disposed intermediate the ends of the piston and is formed in two portions, one of which, designated 66, may besaid to be an annular rectangularportion and the other of which, designated 61, `may be said to be an annular triangular portion. The

former forms the major portion of the groove and the latter the minor portion thereof. It will be noted that thetapered portion 61 of the groove lconnects into the openjportion of the groove 66 `on the side toward the pressure zone of the cylinder. The bottom of thetriangular groove` por- "tion 61 is inclinedtoward the bottomof the `rectangular portion 66. 'Ihe packing ring normally "has a shape substantially like that of the groove 66 and is designed so that .its axial dimension is the same as the axial dimension of the groove 66,

but its radial extent is greater than the radial exo `te`nt of the groove 66. Thus, the inner diameter of thepackingring 651s `lessthan the inner diameter of the rectangular groove portion 66. Hence,` the mass of `the packing ring is greater than the volumetric capacity of the rectangular groove portion 66' so` that normally the packing the pressure zone to occupy the `relieved portion of the groove. This construction has been found by exhaustive tests to provide a very effective seal against leakage of the braking uid past the .pis-

ton. i i

When the braking fluid is delivered yto the wheel cylinder 50 under `pressure to force the pistons 5|` outwardly, this motion :is transmitted from the two-part thrust devices 51, 6I tothe brake shoe lugs 23 thereby moving the split ends of the shoe outwardly into engagement with the drum while at the same time expanding the shoe as a whole against the` drum. As vsoon, as contact between the shoe and drum is eiiected the rotation of the drum tends `tohrotate the .brake shoe in the same direction, as for instanceshown At the same time the energizing link 31 tilts or rocks about the portion 32 of the lever. The re'- 'sult of this compound action `is theapplication of an outward force through lever arm v36 to the `brake shoe at one side of the anchor/pin'and `also the application of an outward reaction force through the link end4 39 and lug 2| to theibrake shoe at the opposite side of the pin;v Two rather Widely spaced substantially` equal pressure points are thus produced at the side of the brake drum opposite to the wheel cylinder. It will be seen,

therefore, that operation of the hydraulic actuator produces two pressure points adjacent` the `ends ofthe shoe,v at which points' the pressure is "substantially'uniform, and also two "similar pressure points spaced substantially as far apart at `the opposite side of the shoe, the energizing 1mi:

and rockable lever which produce the pressures at these latter points being responsive to` the brake application force and energized by rotationalmovement of lthe shoe.

, It will be understood that a similar but reverse action will take place when the brake drum rotates; in the opposite or clockwise direction and the brake is; applied. Insuch instance the. pressure points intermediatethe split: ends of. the shoe will` be; at the points ofV contact. of, thev arm 35 and p ortion 4.0 of the link with the brake shoe when the lever andv energizing lin-lg are rocked in the opposite direction4 from that shown in Fig. 3.

Ihe invention thus provides a brake in which the brake shoe is pressed against the drum under a substantially uniform pressure, outward forces upon the shoe being simultaneously applied to the shoe at four widely spaced points. Hence, a brake of great efficiency is provided in which the eiort required to operate the brake is reduced, the life of the brake lining materially increased, and smoother andmore positive braking action under all conditions achieved.

I claim:

1,. In a brake, in combination, a brake drum, a brake shoe adapted for engagement with the drum, a backing plate, mea-ns for applying a force to one end of said shoe to bring the` shoe into engagement with the drum, an anchor pin mounted upon the backing plate, a rockable member carried by said pin and having its ends engageable with said brake shoe, and an energizinglink associated with said member andhaving its ends-engageable With the shoe, said member and link providing means for transmitting said force to the shoe at spaced points remote from said end of the shoe.

2. In a brake, in combination, a brakev drum, a brake shoe adapted for engagement with the drum, a backing plate, means for applying a force to-one end of said shoe tobring the shoe into engagement with the drum, an anchor pin mounted upon the backing plate, a rockable member carried by said pin and having its ends engageable with said brake shoe, and an energizing link associated wtih said member and having its ends engageable'with the shoe at points spaced from the points of engagement of the rockable member with the sh'oe, said member and` link providing means for transmittingsaid force to the shoe at a plurality of points all remote from said end of the shoe.

3. In a brake, in combination, a brake drum, a Vbrake shoe adapted for engagement with the drum, a backing plate, means for applying a force to one end of said shoe to bring the shoe into engagement with the drum, an anchor pin mounted upon the backing plate, a rockable member carried by said pinand having its ends engageable with said brake shoe, and an energizing link associated with said member. and having .its ends engageable with the shoe at points beyond the ends of the rockable member, said member and link providing means for transmitting said force to the shoe at a plurality of points all remote from said end of the shoe.

4. In a hydraulic brake, in combination, a brake drum, a brake shoe adapted for engagement with the drum, ay backing plate, hydraulically operated means for applying a force to one.

end of the shoe to bring the shoe into engagement with the drum, an anchor pin mounted upon the backing plate, a rockable member carried by said pin and` having its ends engageable with said brake shoe, and an energizing member associated with said rockable member and having its ends engageable with the shoe, said members being adapted to be rocked in opposite directions about the, pinv .intol engage-l ment` with the shoev to transmit said force tothe Kshoe simultaneously at opposite sides of said pin when the brake is applied.

5. Inv a4 brake, in combination, a brake drum, a brake shoe adapted for engagement with the drum, a backing plate, means for applying a force to one end of the shoe to bring the shoe into engagement with the drum, an anchor pin mounted upon the backing plate, a rockable member carried by said pin and having its ends engageable with said brake shoe, and an energizing member associated with said rockable member and having its ends engageable'with the shoe, said members being adapted to be rocked in opposite directions about the pin into engagement with the shoe to transmit said force to the shoe simultaneously at opposite sides of said pin when the brake is applied.

6. In a brake, in combination, a brake drum, a brake shoel adapted for engagement with the drunr, a backing plate, means for applying a force to one end of said shoe to bring the shoe into engagement with the drum, an anchor pin mounted upon the backing plate, a rockable member carried by saidk pin and having its ends engageable with said brake shoe at opposite sides of the pin, spaced lugs on the inner face of the shoe at opposite sides of said pin, and an energizing member associated with said rockable member and having its ends engageable with said lugs, said' first member being rocked in one direction to engage the brake shoe at one side of the anchor pin, and said second member being rockedin the opposite direction and' engaging a lug at the other side of said pin, whereby to transmit the force to the shoe at two spaced points remote from said end of the shoe when the brake is applied.

'7. In a vehicley brake, in combination, a brake drum, a brake shoe, means for applying a force to one end of the shoe to bring the shoe into engagement with the drum, and means responsive to the action of said force to simultaneously press the shoe against the drum at a plurality of spaced. points locatedrelatively remote from said end of the shoe, said means comprising a pair of relatively rockable members, one mounted to rock `upon the other andthe latter pivotally mounted upona stationary partof the brake.

8. In a. vehicle brake, in combination, a brake drum, a transversely split brake shoe, means for effecting engagement of the shoe with the drum by the` application of a force to the ends of the -shoe thereby causing a rotational movement of the shoe in response to the rotation of the drum, a rockable member pivotally mounted on the brake, and a movable energizing member superimposed and tiltable upon the rockable member in end thrust engagement with the shoe and responsive to said rotational movement of the shoe for rocking said member to cause said membery toapply pressure to the shoeV at one point and also eiectiveto` apply pressure to the shoe at its point of end. thrust engagement therewith. 9. In a vehicle brake, in combination, a brake drum, a transversely split brake shoe, means for eiecting engagement of the shoe with the drum by the application of a force to the ends of the shoerthereby causing a rotational movement of the shoe in response to the rotation of the drum, a rockable member pivotally mounted on the brake, and a movable energizing member superimposedupon. therockable member in end thrust engagement with the shoe and responsive to said rotational movement of the` shoe for rocking said member to cause said-memberto apply pressure to the shoe at one `point and also effective to apply pressure to the shoe at its point of end thrust engagement therewith, said energizing member being adapted to tilt or rock in a direction opposite to the movement of therockable member when the brake is applied. 4

10. In a vehicle brake, in combination, a brake drum, a transversely split brake shoe, means for e effecting engagement of the shoe with the drum y by the application of a force to the ends of the shoe thereby causing a rotational movement of the shoe in response to the rotation of the drum, a rockable member pivotally mounted on the brake, and a movable energizing member superimposed upon the rockable member in end thrust engagement with the shoe and responsive to said rotational movement of the shoe for rocking said member to cause said member to apply pressure to the shoe at one point and also effective to apply pressure to the shoe at its point of end thrust enlgagement therewith, said energizing member having its pressure point on said brake shoe at the 4side of the pivot of said rockable member opposite to the pressure point of the y rockable member when the brake is applied.

GEORGE JOSEPH THOMAS@ 

